The invention is based upon bio-compatible polyurethane based upon cyclo aliphatic diisocyanates, aliphatic and/or cyclo aliphatic macrodiols and lower-molecular aliphatic and/or cyclo aliphatic diols, which if necessary are dissolved in a solvent, the process for the production thereof as well as the employment of these polyurethanes for the production of bio-compatible shaped bodies.
Polyurethanes have been known for a long time and are prepared according to the most different techniques. Thus, for example, a macrodiol can be reacted with diisocyanate into a pre-adduct, the pre-adduct then being further reacted with one or more lower-molecular diols for the purpose of chain lengthening. It is also to react diisocyanate, macrodiol and chain lengthener simultaneously according to the so-called one pot process.
A distinguishing factor characteristic of polyurethane as compared to other synthetic materials is that they are relatively bio-compatible, i.e., they are extensively accepted by human or animal bodies, thus being compatible with the body and in particular displaying blood- and tissue-compatibility.
The heretofore bio-compatible polyurethane display, however, a series of disadvantages. On the one hand, they become disadvantageously influenced by hydrolytical factors within a more or less brief period of time whereby the mechanical characteristics, such as tensile strength, elongation and elasticity are affected, many polyurethanes thus indeed being completely decomposed within the course of time.
The above described deficiencies are also disadvantageously perceptible with bio-compatible shaped bodies if they are composed of such polyurethanes.
It is also known to manufacture so-called vessel prostheses in the form of tubing or thin tubules by means of the spinning of fibers from polymer solutions, transportation and laying down of fibers onto the rod or stick-shaped substrate so as to provide a fleece.
A technique is thus described in European patent 5035, for example, whereby the polymer solution is spun by means of the so-called electrostatic spinning process. An entire series of polymers is recommended as spinning solution for the manufacture of these plastic vessel prostheses, such as polyamide, polyacrylonitrile, polyurethane. In addition, polymers such as polytetrafluorethylene which can be worked up as a dispersion should be employable according to the teachings of this European patent.
A further process for the preparation of such vessel prostheses is described in DE-OS 28 06 037, according to which the prostheses are formed by means of fiber or filament spraying from a polymer solution. The reference sets forth in its Examples various market-accessible polyurethanes. Also with these techniques the above described disadvantages of polyurethane are observed.
When also the technology for the production of vessel prostheses has already been developed according to the most different techniques such as e.g., through preparation of fibers or filaments and a laying down thereof onto a rod or stick into a fleece or by means of extrusion of a solution, the behavior of the synthetic vessels in human or animal bodies depends not only upon the techniques with which the working up of the polymers have been implemented, but even the polymer itself plays a completely distinguishing role, moreover its chemical construction and in particular the manner of the preparation thereof.